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ENERGY TRANSITION

Figure 1 - Open Cycle Gas Turbine and LM2500+G4 GTG
“Lean Package”

On the other hand, gas turbines emit large
amounts of high temperature exhaust gases
(>500°C) to the atmosphere, with consequent
losses of heat and CO emissions. In Offshore,
2
Additional projects for FPSO applications are either the hot exhaust gases can also be recovered by
under construction (such as on the Bacalhau field means of a Waste Heat Recovery Unit (WHRU)
in Brazil) or being planned in other sites across the for heating a transfer fluid used for process pur-
globe and especially in Latin America [3]. poses, not for electrical efficiency increase. To
This paper focuses on the CCGT solutions adop- raise the OCGT efficiency up to 42%, a higher
ted on the FPSOs highlighting Baker Hughes ex- power range gas turbines family, the aero-deri-
perience and the main technical constraints and vative LM6000 (40-54 MW ISO) can be levera-
considerations to be taken into account when de- ged while still maintaining low weights and foot-
signing such a technology. print. For a further electrical efficiency increase it
is necessary to consider a CCGT.

Open Cycle Gas Turbines
Combined Cycle Overview

On a FPSO, the production of power with OCGTs
(Figure 1) is typically the solution of choice. Gas Leveraging its process and plant design compe-
turbines have the advantage of high power density tences, on top of its experience as OCGT sup-
and flexibility. OCGTs can be used in turbogenera- plier for Offshore installations, Baker Hughes is
tors for base and emergency auxiliary services, or currently engaged on a number of CCGT plants
also directly to drive compressors and pumps. Gas for FPSO and is executing world’ first of such a
turbines are not very restrictive in terms of loading kind.
and unloading rates and are capable to start-up
fast for on demand plant needs. They require only Looking at deep water projects,
ambient air as combustion medium, and a combu-
stible, normally the abundant and economic natural power generation is the biggest
gas produced from the reservoir. “emission contributor on an FPSO
Offshore, the gas turbine selection of choice is the plant, with more than 60% of
aero-derivative technology such as Baker Hughes
LM2500 family, which leverages hundreds of instal- the total greenhouse gas (GHG)
lations and millions of operating hours. LM2500 emitted during lifecycle
family is designed for high efficiency (>40% in ISO
conditions), reliability and availability in the 25-38
MW range. Its Gas Turbine Generator (GTG) packa- The CCGT solution significantly improves electrical
ge is designed to minimize footprint and weight (Fi- efficiency as it is capable to reduce up to 20% or
gure 1), two critical parameters Offshore. more the overall emitted CO per MWh produced
2

28 Impiantistica Italiana - Maggio-Giugno 2024